Scour detection at bridge piers and the like

ABSTRACT

Apparatus for measuring bottom scour at structures in the water, such as bridge piers, abutments, retaining walls, dams, locks, drilling rigs, lighthouses and radar platforms, A plurality of electroacoustical transducers on the structure at spaced locations and directed toward the bottom, with means for periodically energizing a transducer at each location and means for determining transit times to the bottom and return. The transit times can be viewed, recorded and compared, with differences in transit times providing a measure of scour at the bottom.

United States Patent Inventor Frederick George Herbert Oakton, Va.

Appl. No. 879,301

Filed Nov. 24, 1969 Patented Nov. 2, 1971 Assignee Data-DesignLaboratories Cucamonga, Calif.

SCOUR DETECTION AT BRIDGE PIERS AND THE LIKE 8 Claims, 4 Drawing Figs.

[1.8. CI 340/3 R lat. G015 9/68 Field of Search 340/], l L,

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UNITED STATES PATENTS ,2,6 29,082 2/1953 Hare 340/1 PrimaryExaminer-Richard A. Farley Ati0rney--Harris, Kiech, Russell & KernABSTRACT: Apparatus for measuring bottom scour at structures in thewater, such as bridge piers, abutments, retaining walls, dams, locks,drilling rigs, lighthouses and radar platforms, A plurality ofelectroacoustical transducers on the structure at spaced locations anddirected toward the bottom, with means for periodically energizing atransducer at each location and means for determining transit times tothe bottom and return. The transit times can be viewed, recorded andcompared, with differences in transit times providing a measure of scourat the bottom.

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FREQUENCY 661 5 05C/LLATOR l I I I H 50/0 TRANSDUCER 1 TRANSDUCER 2TRANSDUCER b TRANSDUCER 4" h w N0. 1 DELAYED 0.!248 5EC.-

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N0. 3 DELAYED 0.04/0 55c.-

m i/EN' r02 FREDDQ/c 650265 f/EQDER?" BY HIS ATTOE/VE Y5 HARE/5 Mac/1,Russ/ELL 6: KEEN 1 scoua nsrscr on aaipcsrisas AND "ma LIKE Thisinvention relates to the measurement of bottom scour at structures inthe water and will be described herein as applied to a bridge pier in ariver. Of course, it is equally applicable to other structures in thewater, such asa'butments, retaining walls, dams, locks, drilling rigs,lighthouse foundations, radar platforms and the like.'

The measurement of bottom scour around bridgepiers and the like isdesired by agencies charged with the responsibility of maintenance ofbridges and similar structures. Itis particularly desirable to have thecapability of measuring bottom scour during periods of high water andrapid river currents. During such periods, the water is often very cold,strongly turbulent and full of debris.

In the past, bottom scour has been measured by visual inspection usingunderwater divers, photographic and television means. It is an object ofthe present invention to provide for the detection and measurement ofbottom scour without requiring bridge inspectors to enter the water oroperate from a boat. A further object is to provide for automatic scourdetection and to provide for detection and measurement during periodsofflood or ice. Y

The present invention contemplates electroacousticaltransducers atspaced locations along the s tructure and normally below the surface ofthe water; Bottom depth at each location is measured by means ofultrasonic beam transmitted, and received by the transducer. The traveltime ortransit time of the signal from the transducer to the bottom andreturn provides a measure of the distance of the bottom from thetransducer location. The electronic equipment provides detection ofscour by energizing transducers at various locations and comparing thedepth measured by the transducers. The pulse data produced by thetransducers may be manipulated, recorded and displaced locally at thebridge pier and/or at remote locations, providing continuous monitoringof conditions'at the bottom. The apparatus is not adversely affected byflooding conditions or ice.

Other objects, advantages, features and results will more fully appearin the course of the following description. The drawings merely show andthe description merely describes preferred embodimentsof the presentinvention which are given by way of illustration or example.

In the drawings:

FIG. 1 illustrates a bridge pier with a plurality of transducers mountedthereon;

FIG'. 2 is an' enlarged view of a portion of FIG. 1 illustrating theinstallation of one of the transducers;

FIG. 3 is a diagram illustrating the electrical system of a preferredembodiment of the present inventiomand FIG. 4 is a diagram illustratingthe timing of the circuitry of FIG. 3.

In the structure illustrated in FIG. 1, transducer units are mounted atspaced locations on a bridge pier 11 at a level between the watersurface 12 and the bottom 13 In the embodiment illustrated in thedrawings, four transducers are utilized, one on each side of the pier,however only three show in FIG. 1. Electrical wiring froni each of thetransducer units runs to a junction box through conduit 2 nd all of thewiring runs up the pier through another conduit 12.

A typical example of bottom scour aboutthe pier 11 is illustrated at inFIG. 1.

A transducer unit is illustrated in greater detail in FIG. 2 andincludes an electroacoustical transducer 27, which may be ofconventional design, mounted on a bracket 28 within a tubular guard 29.The guard 29 is supported on pipes 30, 31 affixed to a mounting plate 32which in turn is bolted to the bridge pier I]. The electrical cable 35from the transducer passes through the upper pipe 31 to the junction box20 and the vertical conduit 22.

Each transducer 21 typically may be a 200 kHz. piezoelectrio ceramictransducer. The guard 29 is open at both ends and does notaffect theaction of the transducer, but serves to pro tect it from debris in thewater. The transducers preferably are installed below the minimum waterlevel and below the expected freeze level. While the embodimentillustrated utilizes four transducers at spaced locations, variousnumbers of transducers can be used as desired for a particularinstallation. In an alternative arrangement, a single transducer couldbe used and a mechanism provided for moving the transducer from locationto location along the structureLWhile this would effect a cost saving intransducers, the cost and maintenance of the transducer moving mechanismwould outweigh this saving in most'situations.

, In a typicalinstallation, the wiring from the four transducers at abridge pier terminates in a connector'box 40 (FIG. 3) located at theroadlevel of the bridge.'The remainder of the apparatus may be located atthis point and plugged in at the connector box, or the connector box maybe omitted, with the ,transducers connected directly to the remainder ofthe apparatus. Alternatively, the remainder of the apparatus may bepositioned at a'remote location and be connected'to the connector box 40by suitable cabling. The remote location'may be at one end of thebridge, or at a central location where a plurality of bridges aremonitored, or elsewhere as desired; In one typeof installation, theapparatus may be portable and an inspector may carry. the apparatus fromone connector box to another for. checkingthe condition at each ofseveral piers or other structures.

The circuitry of FIG. 3 includesa timing generator 4], an

oscillator 42, atransducer switching unit43, amplifiers 44 and ,45 and apulse-forming unit 46; Various types of display and recording devicesmay be usedsingly or in combination, and four are illustrated in FIG. 3.

The output of the pulse-forming unit 46 may be connected to a counter 50and a DC readout 51. The output of the unit 46 may be connected to apower. amplifier 52 andrecorder 53. The output of the unit 46 may beconnected to a video display 54. The output of the unit may also beconnected through a delay 55 to a comparator 56 and alarm 57. Theoutputof the delay 55 may also be connectedtothe video display 54.

The circuitry of FIG. 3 and the timing diagram of FIG. 4 utilize fourtransducers, which are identified as I, 2, 3, and 4.

The circuitry of FIG. 3 provides for automatically energizing thetransducers, processing the received data, and recording and displayinginformation representing bottom scour. TIIe circuitry of FIG. 3 providesfor energizing each of the transducers in sequence. In analternativearrangement, all

transducers could be energized at the same tiineflbut this,

would require separate circuitry for handling each: transducer with aresultant increase in cost and size.

The timing generator 41 produces two signals, trigger pulses 60 for theoscillator 42 and timing pulses 61 for the delay 55. As seen in FIG. 4,there are four trigger pulses for each timing pulse, with a timing pulsecoinciding with one of the trigger pulses. A combination 62 of thetrigger and timing pulsesis provided for the transducer switching unit43.

The oscillator 42 oscillates a few cycles at the transducer frequency(200 kHz.) on receipt of each trigger pulse. The oscillator supplies thenecessary pulse power for energizing a transducer. The oscillator outputis connected to a transducer 27 by the transducer switching unit 43. Thetransducer switching unit connects transducer 1 to the oscillator eachtime the unit receives a timing pulse. On receipt of the next triggerpulse, the switching unit connects transducer 2 'to the oscillator.Similarly, transducers 3 and 4 are connected to the oscillator with eachof the following trigger pulses.

With transducer 1 connected to the oscillator, the pulse power from theoscillator causes the transducer to oscillate and transmit an ultrasonicsignal toward the bottom. A portion of the signal energy is reflectedfrom the bottom back to the transducer, with the remainder of the energybeing scattered or absorbed. This small received signal or echo is sentfrom the transducer through the switching unit to the oscillator andthen through the two stages of amplification. The oscillator output isillustrated at 65 and the echo signals are illustrated at 66. Both theoscillator output pulses and the echoes pass through the amplifiers andare illustrated at 67 and 68. The oscillator pulse signals and theechoes for each of the four transducers as actuated in sequence are seenin 65-68.

The time difference between an oscillator pulse and the echo pulse for aparticular transducer will be a measure of the water depth from thetransducer to the bottom directly below the transducer. This timeinterval may be manipulated in various ways to provide various types ofrecords and displays for the depth information.

After amplification, the 200 kHz. pulse signals may be converted to DCpulses 72 in a pulse-fonning unit 46, with these pulses maintaining thesame time difference between each oscillator output pulse and its echo.The recorder 53 may be a typical strip chart recorder with the recordpaper moving at a constant speed. Distance along the chart may becalibrated directly in depth in feet so that the difierence on the chartbetween an oscillator pulse and an echo can be read directly in feet. Ifbottom sour is present, the depth at the location of the scour will begreater than the depth at the other transducers and can be readily seenfrom the recorder chart.

The pulse pattern 72 may also be presented on an oscilloscope in thevideo display 54. Difi'erences in transit time at the varioustransducers may be noted visually, providing an indication of theexistence and location of scour.

The counter 50 may measure the time lapse between an oscillator outputpulse and the echo. This time may be displayed on some type of readoutmeter, including a numerical presentation, and may be calibrated to readdirectly in depth.

In the delay unit 55, incoming pulses are transmitted to the output witha predetermined amount of delay so that the pair of pulses for onetransducer will be presented to the comparator 56 at the same time asthe pair of pulses for another transducer. In the particular embodimentillustrated, the pulses for the fourth transducer are not delayed andthe magnitude of delay for each of the other three transducers isindicated in the timing diagram of FIG. 4 for the particular frequenciesutilized. The timing pulse output from the timing generator serves tomaintain the delay unit is synchronism with the transducer switchingunit. The output of the delay unit may be presented directly on theoscilloscope of the video display, and could have the appearance of thebottom four lines of FIG. 4 when there is no scour. By way of example,if scour existed under transducer 3, the right pulse in the bottom linewould be further to the right than in FIG. 4, indicating a greatertransit time for the ultrasonic signal and a greater depth of waterbelow the transducer. The comparator 56 functions to compare the timebetween oscillator pulse and echo for each of the four transducers andactuate an alarm 57 when there is a difference of some predeterminedmagnitude. The alarm might be a light or a signal or a chart indicationor any other conventional device.

The apparatus of the invention can be used to detect bottom scour atstructures in the water of rivers, lakes, seas and the like. It isprimarily intended for detection of river bottom scour around bridgepiers but is also useful with other structures in the water includingabutments, retaining walls, dams, locks, drilling rigs, lighthouses andradar platforms. While the embodiment illustrated provides for automaticand periodic actuation of each of the transducers, the switching couldbe performed manually in a simplified system. Although exemplaryembodiments of the bottom scour system have been disclosed, it will beunderstood that other applications of the invention are possible andthat the embodiments described herein may be subjected to variouschanges, modifications and substitutions without necessarily departingfrom the spirit of the invention.

lclaim:

1. ln apparatus for measuring bottom scour at a structure in the water,the combination of:

transducer means including at least one electroacoustical transducer;means for mounting said transducer means on the structure,

said transducer means including means for directing acoustical signalsto the bottom from spaced locations along the structure;

means for periodically energizing a transducer at each of saidlocations, with a portion of the signal reflected from the bottom to thetransducer; and

means for determining the travel time of a signal from transducer tobottom and return to transducer for each of said locations, withdifferences in the travel times providing a measure of scour at thestructure.

2. Anapparatus as defined in claim 1 including means for comparing thetravel times for two locations and providing an indication when saidtravel times difi'er by more than a predetennined amount.

3. An apparatus as defined in claim 1 in which said transducer meansincludes a plurality of electroacoustical transducers, with a transducerat each of said locations.

4. An apparatus as defined in claim 3 in which said means for energizingincludes means for energizing each of said transducers in sequence.

5. An apparatus as defined in claim 1 in which said means fordetermining travel times includes means for generating a visual displayof the travel times.

6. An apparatus as defined in claim 3 in which said means forperiodically energizing includes;

a timing generator for generating a trigger pulse for each of saidtransducers in sequence;

an oscillator for generating a transducer driving signal for eachtrigger pulse;

a transducer switching unit for connecting the oscillator driving signalto each transducer in sequence and in synchronism with said triggerpulses; and

circuit means for connecting said trigger pulses to said oscillator andsaid switching unit.

7. An apparatus as defined in claim 2 in which said means for energizingincludes means for delaying the signal at one location relative to thesignal at another location by a predetermined time, and

in which said means for comparing includes means for delaying theearlier of said travel times by said predetermined time.

8. An apparatus as defined in claim 1 in which said means for energizingincludes means for delaying the signal at one location relative to thesignal at another location by a predetermined time, and

in which said means for determining includes means for generating avisual display of the travel times, and means for delaying the earlierof said travel times by said predetermined time so that the travel timesare displayed at the same time.

1. In apparatus for measuring bottom scour at a structure in the water,the combination of: transducer means including at least oneelectroacoustical transducer; means for mounting said transducer meanson the structure, said transducer means including means for directingacoustical signals to the bottom from spaced locations along thestructure; means for periodically energizing a transducer at each ofsaid locations, with a portion of the signal reflected from the bottomto the transducer; and means for determining the travel time of a signalfrom transducer to bottom and return to transducer for each of saidlocations, with differences in the travel times providing a measure ofscour at the structure.
 2. An apparatus as defined in claim 1 includingmeans for comparing the travel times for two locations and providing anindication when said travel times differ by more than a predeterminedamount.
 3. An apparatus as defined in claim 1 in which said transducermeans includes a plurality of electroacoustical transducers, with atransducer at each of said locations.
 4. An apparatus as defined inclaim 3 in which said means for energizing includes means for energizingeach of said transducers in sequence.
 5. An apparatus as defined inclaim 1 in which said means for determining travel times includes meansfor generating a visual display of the travel times.
 6. An apparatus asdefined in claim 3 in which said means for periodically energizingincludes: a timing generator for generating a trigger pulse for each ofsaid transducers in sequence; an oscillator for generating a transducerdriving signal for each trigger pulse; a transducer switching unit forconnecting the oscillator driving signal to each transducer in sequenceand in synchronism with said trigger pulses; and circuit means forconnecting said trigger pulses to said oscillator and said switchingunit.
 7. An apparatus as defined in claim 2 in which said means forenergizing includes means for delaying the signal at one locationrelative to the signal at another location by a predetermined time, andin which said means for comparing includes means for delaying theearlier of said travel times by said predetermined time.
 8. An apparatusas defined in claim 1 in which said means for energizing includes meansfor delaying the signal at one location relative to the signal atanother location by a predetermined time, and in which said means fordetermining includes means for generating a visual display of the traveltimes, and means for delaying the earlier of said travel times by saidpredetermined time so that the travel times are displayed at the sametime.